空间数据库在当前的地理信息系统(GIS)应用中具有非常重要的地位,空间数据引擎(SDE)技术则以附加中间层较好地解决了GIS功能应用与数据库集成中数据提供与访问模式方面的制约瓶颈问题,并在“湖北省水土流失动态络系统”构建综合数据库的应用中取得良好效果。-Spatial databases in the current geographic information systems (GIS) applications with a very important position, spatial

带时间特性和空间特性的角色授权管理模型是在现有的RBAc研究,4J的基础上,对角色加入时间约束和空闻约束,引入角色级别和用户级别的概念,提高系统的安全性和灵活性,降低授权管理的复杂性,并解决了相互冲突的角色的授权问题。-Time characteristics and spatial characteristics with the role of authorization management model is the existing RBAc research, 4J, based on

MU-MIMO is widely considered a key technology for system capacity improvement in modern wireless networks. In contrast to SU-MIMO, where the spatial multiplexing gain is confined to a single user, MU-MIMO allows multiple users to be co-sche